1. Field of the Invention
This invention concerns an improved process for the preparation of urethanes (carbamates) by reacting a primary or secondary amine with carbon monoxide, an alcohol, an oxidant, and a catalyst.
2. References
U.S. Pat. No. 3,405,156 discloses a process for the production of isocyanates comprising reacting an amine with carbon monoxide and a platinum group metal including platinum, palladium, and rhodium. Regeneration of the platinum group metal is disclosed employing polyvalent metal compounds including halides and acetates of copper, mercury, cerium, iron, cobalt and the like, preferably cupric chloride and ferric chloride.
Durand et al., Tetrahedran Letters (1969) 28, 2329, and 2330, disclose the effect of various phosphines on selectivity in the carbonylation of amines to formamides and ureas catalyzed by rhodium complexes.
U.S. Pat. No. 3,641,092 discloses conversion of an organic amine to an isocyanate by reaction of the amine with carbon monoxide in contact with palladium chloride. The catalyst can be regenerated with oxygen or in admixture with copper chloride and oxygen.
U.S. Pat. No. 4,251,667 discloses the preparation of aromatic urethanes by reaction between aromatic amines, alcohols and carbon monoxide using copper salts, preferably copper halides, as catalysts. In a regenerating copper catalyst system, an oxygen-containing gas and a dehydrating agent are employed. Copper(II) acetate can be employed.
U.S. Pat. Nos. 4,260,781 and 4,266,070 disclose the preparation of carbamates in which an organic amine is contacted, in the substantial absence of reactive oxygen, with carbon monoxide, an alcohol, and a molar quantity of a Group VIII metal compound or complex or selected metal carbonyls.
U.S. Pat. No. 4,227,008 discloses that aromatic urethanes can be produced by interacting an aromatic primary amino compound having a nitro group, a nitroso group or a carbamate group, an organic compound having at least one hydroxyl group, and carbon monoxide in the presence of a catalytic system composed of a platinum group metal and/or a compound thereof serving as a catalyst and a Lewis acid and/or a compound thereof as promoter under high temperature and pressure. Examples of Lewis acids given include acetates among possible anions and copper among possible metals.
EP No. 71,835 discloses the preparation of a carbamate by reaction of a urea with carbon monoxide, an alcohol, molecular oxygen, a Group VIII metal catalyst, and a quinoid oxidizing agent, optionally in the presence of a metal redox compound such as copper(II) acetate.
Fukuoka et al., J. Chem. Soc., Chem. Commun. (1984), 399 and 400, describe the oxidative carbonylation of amines by carbon monoxide, oxygen and alcohols to give carbamates using a palladium and iodide ion catalyst system.
Fukuoka et al., J. Org. Chem. (1984) 49, 1458 to 1460, describe the oxidative carbonylation of amines by carbon monoxide, oxygen and alcohols to give carbamates using a platinum group metal and alkali metal halide or onium halide catalyst system.
Narain, Canadian Journal of Chemistry, 44, 895 (1966), describes the preparation of coordination complexes of copper(II) acetate, ammonia, aliphatic amines, and pyridine. For the copper(II) acetate amine complexes disclosed, the molar ratio of amine to copper(II) in the complexes is 2:1.
Kokot et al., Inorganic Chemistry, 3, 1306 (1964), describe the preparation of amine copper(II) complexes wherein the molar ratio of amine to copper(II) is 1:1.